The hospital records of the selected admissions were reviewed by a team of 66 nurses and 55 medical specialists. The eligibility criteria for medical specialists to act as a reviewer were: more than 10 years post graduate general clinical experience; a good reputation among colleagues; that they had been retired for no longer than 5 years; that they had experience or affinity with the analysis of incidents, complaints and errors in clinical care; and that they were available for at least one day per week.
An additional expert panel of 18 medical specialists from several sub specialties was recruited to offer expert advice about accepted clinical practice during the review process. These specialists were authorities within their specialization and were recruited by the scientific associations of medical specialists. The panel consisted of specialists from all medical disciplines involved in the study.
The nurses and medical specialists followed a one-day training course in small groups comprising a maximum of 12 participants led by one researcher and one experienced nurse or medical specialist, respectively. During the training, the study protocol, definitions, and electronic review forms were explained and examples of AEs were discussed. The reviewers practiced on examples of cases and with the review forms. They were provided with a review manual in which the research protocol, instruments, and definitions were defined . After one month of reviewing, they undertook a half-day training session to discuss their problems concerning the review process. The reviewers were also updated with the latest insights about the review process. These training sessions were repeated frequently during the data collection period. The problems discussed were collected and noted in a regularly updated Frequently Asked Questions (FAQ) document, which was distributed to all reviewers.
Structured review of patient records
The nursing, medical and, if available, outpatient records of the 7,926 sampled hospital admissions were reviewed in a three stage review process. In the first stage, the nurse reviewers screened the records by using 18 explicit screening criteria indicating potential AEs (Appendix A).
In the second stage of the review process, two medical specialists independently reviewed the records screened positive by the nurses in stage one (4,317 patient records). During the previous stage, nurses indicated which medical specialty would be most suitable for reviewing each particular record. Two physician reviewers from the specialty indicated reviewed each record independently and determined whether an AE had occurred.
Records with screening criteria concerning surgical care were reviewed by two surgeons. They used a standardized procedure with a structured electronic review form to determine whether an AE had occurred and to what degree it was preventable. The determination of an AE was based on three criteria: (1) an unintended physical and/or mental injury; which (2) resulted in temporary or permanent disability, death or prolongation of hospital stay, and; was (3) caused by health care management rather than the patient's disease (Appendix A) [1–3, 8, 17]. Preventability was defined as care that fell below the current professional standards and expected performance for practitioners or systems. Preventability was measured on a six-point scale (one = no preventability and six = definite preventability). Consistent with most previous international studies, we used a score of one to three to indicate that AEs were not preventable and a score of at least four to indicate that AEs were preventable .
If there was disagreement about the presence and/or preventability of an AE between the two independent surgeon reviewers, they started a procedure to achieve a consensus (stage 3). If the two surgeons could not reach a consensus, a third surgeon reviewer with access to all the information determined the final judgment.
If an AE was identified, the consequences, most responsible specialty, causes and potential prevention strategies were assessed. Surgical AEs were defined as AEs attributable to surgical treatment and care processes. The surgeon reviewers classified the surgical AEs by clinical procedure involved, such as diagnostic process, surgical procedure, drug/fluid, medical procedure, other clinical management, discharge, and other. The consequences were defined as: a prolonged hospital stay, extra treatment, a readmission to the hospital, extra outpatient care, a temporary or permanent disability at discharge, and death as a result of an AE. The consequences of surgical AEs were also classified by the type of injury, such as: bleeding, infection, shock, thrombosis, necrosis, fistula forming, and abnormal wound healing. The classification by injury was according to the national reporting system of adverse outcomes developed by the Association of Surgeons in The Netherlands [19, 20]. For each AE, the reviewers indicated all consequences.
In addition, the underlying causes
of AEs were assessed. An AE arises often due to several causal factors, including technical, organisational, human, and patient-related factors. For each AE, the surgeon reviewers selected one or more causes. The reviewers selected all causes that contributed to the occurrence of the AE. They used a recognized taxonomy of root causes: the Eindhoven Classification Model of PRISMA-Medical, a root cause analysis tool [21
]. The categories of the taxonomy are:
Human factors which are, skill-based, for example failures in the performance of highly developed skills, or, rule-based, for example an incorrect fit between an individual's training or education and a particular task, or knowledge-based, for example inadequate application of existing knowledge;
organizational factors, for example inadequate or unavailable protocols, management priorities, inadequate transfer of information and cultural aspects;
technical factors, for example material defects, failures due to poor design of equipment, software, labels or forms;
patient-related factors, for example, co-morbidity, age, and treatment compliance .
Finally, for all preventable AEs, potential prevention strategies were selected. The categories were based on PRISMA and the Canadian patient record review study [1, 22]. The review form distinguished ten prevention strategies: quality assurance/peer review, training, evaluation, procedures, motivation, information and communication, technology/equipment, personnel, scaling up, and financial investment. For each AE, the surgeon reviewers could select one or more potential prevention strategy. The reviewers selected the causes and potential prevention strategies based on information in the patient record and on their perception of the situation .